What does "alliteration" mean?

Alliteration: The repetition of the same letter at the beginning of two or more words immediately succeeding each other, or at short intervals; as in the following lines: - Behemoth, biggest born of earth, upheaved His vastness. Milton. Fly o'er waste fens and windy fields. Tennyson. Note: The recurrence of the same letter in accented parts of words is also called alliteration. Anglo-Saxon poetry is characterized by alliterative meter of this sort. Later poets also employed it. In a somer seson whan soft was the sonne, I shope me in shroudes as I a shepe were. P. Plowman.